The present invention relates to a photosensitive polymer. Especially relates to a photosensitive polymer for using in the chemical amplified photoresist composition.
Current semiconductor industry trends indicate that availability of lithography below 0.18 xcexcm is required for the development of high performance logic processors and 1-Gbit DRAM. In theory, there are two possible ways to get resist patterns with finer resolution, i.e. to shorten the wavelength of exposure light sources and to enlarge the numerical aperature (NA) of exposure systems.
KrF excimer laser (248 nm) steppers are widely used for the 0.25 xcexcm UV lithography manufacturing process of semiconductor devices. Due to the improvement of optical elements such as high NA optical elements, phase shift mask, etc., the 248 nm KrF scanners now are capable of offering pilot run of 0.18 xcexcm process and pioneer development of below 0.15 um process. However, since there is a limit for wavelength shortening, the processing or manufacturing of finer masks becomes more and more difficult. To meet the urge demand of minimizing the size of IC devices, development of 193 nm (ArF excimer laser) lithography and resists are recognized as an alternative resolution recently.
Unfortunately, due to the strong absorption of aromatic rings that provides dry-etch resistance, the conventional chemical amplified resists based on phenol resin (248 nm) are totally opaque at 193 nm. To solve the problems, new polymers that exhibit low optical density at 193 nm are in great need now.
Generally speaking, the polymer which is adequate candidate for the photoresist for 193 nm lithography is required to meet six basic requirements:
(1) high transparency for 193 nm light source;
(2) good thermoplastic, ex. High glass transition temperature (Tg);
(3) high etch resistance;
(4) good adhesion and development for its composition;
(5) contained acid labile functional groups;
(6) be applied to general processes.
Recently, a tetrapolymer iBMA-MMA-tBMA-MMA (poly isobornyl methacrylate-methyl methacrylate -t-butyl methacrylate-methacrylic acid) is reported to be a possible resin system for ArF resist: 
However, the tetrapolymer is also accompanied with undesirable adhesion and etch resistance. Therefore, a new resin for the compositions of resists is eager to be developed.
One object of the present invention is to provide a photosensitive polymer with excellent etch resistance, thermal properties and optical transparence at 193 nm.
The present invention provides a photosensitive polymer containing the following structure unit of formula (II): 
Wherein R is hydrogen or C1-C4 alkyl group; Rxe2x80x2 is C1-C4 alkyl group; n is an integer of 2, 3, 4, 5 or 6.
The photosensitive polymer can be used as components of chemical amplified photoresist compositions. The photosensitive polymer of the present invention can be optionally mixed with photo-acid generators, acid quenchers, additives or solvents to form photoresist compositions applied for general lithography process or 193nm lithographic process.
The photosensitive polymer of the present invention is prepared from the following formula (I) compound: 
Wherein R is hydrogen or C1-C4 alkyl group; Rxe2x80x2 is C1-C4 alkyl group; n is an integer of 2, 3, 4, 5 or 6.
Preferably, compound (I) is a monomer of polycycloalkyl acrylate which can be obtained from the reaction of acryloyl chloride and tricycloalcohol or its derivatives.
Compound (I) can polymerized or copolymerized with other vinyl monomers to form various polymers or copolymers with or without the assistance of catalysts.
There is no special limit for the application of the polymers or copolymers. However, if the polymers polymerized or copolymerized from compound (I) are expected to be transparent for the radiation with 193 nm wavelength, vinyl monomers free of aromatic rings are preferred.
Vinyl monomers suitable to copolymerized with compound (I) can be 
The polymers or copolymers polymerized or copolymerized from compound (I) contain the following structure unit of formula (II): 
wherein R, Rxe2x80x2 and n are defined as the above.
The structure unit of the polymers or copolymers polymerized or copolymerized from compound (I) can be 
in the above structure unit of formula (III), (IV), (VI), (VII) and (VIII) , wherein g+h+i=1, more preferably g/(g+h+i)=0.1-0.5, h/(g+h+i)=0.1-0.5, and i/(g+h+i)=0.1-0.5; in the above structure unit of formula (V), wherein g+h+i+j=1, more preferably g/(g+h+i+j)=0.1-0.5, h/(g+h+i+j)=0.1-0.5, i/(g+h+i+j)=0.1-0.5, and j/(g+h+i+j)=0.1-0.5.
There is no special limit for the synthetical method of the polymers or copolymers from compound (I) of the present invention. Preferably, the polymerization or copolymerization of compound (I) or its mixture is initiated by initiators. Initiator used here can be any initiator used by the people who is skilled in the art. Preferably, the initiator is 2,2xe2x80x2-azo-bis-isobutyronitrile(AIBN) or dimethyl-2,2xe2x80x2-azo-bis-isobutyrate radical initiator (V-601)
The polymers or copolymers of present invention can combine with adequate photo-acid generator (PAG), acid quencher, additives or solvent to form chemical amplified photoresist compositions. The chemical amplified photoresist composition of the present invention can be used in the process of lithography. Especially, the chemical amplified photoresist composition of the present invention can be used in the process of 193 nm (ArF excimer laser) lithography.
More detailed examples are used to illustrate the present invention, and these examples are used to explain the present invention. The examples below, which are given simply by way of illustration, must not be taken to limit the scope of the invention.

(A) Synthesis of 8-methyl-tricyclo[5.2.1.02, 6]decan-8-ol (Formula (X))
Tricyclo[5.2.1.02, 6]decan-8-one (15.0 g) in tetrahydrofuran (THF, 50 ml) is slowly added into CH3MgCl (9.7 g) in THF and the reaction mixture is stirred completely. Tetrahydrofuran (THF, 100 ml) with 5% of water is added into the reaction mixture. Then 100 ml of water is added to the reaction mixture. The reaction mixture is extracted by ether. The organic extract is concentrated in vacuo to yield 8-methyl-tricyclo[5.2.1.02,6]decan-8-ol (formula (X)) as white solid.
1H-NMR (CDCl3, 300 MHz) xcex42.60-2.45 (1H, m), 1.90-1.50 (8H, m), 1.28 (3H, s) 1.40-0.80 (5H, m).
13C-NMR (CDCl3, 75 MHz) xcex476.9, 52.8, 46.8, 46.5, 41.8, 39.3, 32.7, 32.4, 31.8, 30.4, 27.4.
(B) Synthesis of 8-methyl tricyclo[5.2.1.02,6]decan-8-yl methacrylate (Formula (I-1))
Methacryloyl chloride (20.9 g) and triethyl amine (20.2 g) is added to 8-methyl tricyclo[5.2.1.02,6]deccan-8-ol (20.0 g) in dichloromethane (200 ml) and the reaction mixture is stirred completely. Then 20 ml of water is added to the reaction mixture. Separating the CH2Cl2 and water layers, then the water layer was extracted with CH2Cl2 (200 mLxc3x973). The organic layer was combined then wash with water till pH=7, dried over MgSO4 and evaporated to dryness. The residue was purified by flash column on silica gel (n-hexane), the filtrate was evaporated to obtain 8-methyl tricyclo[5.2.1.0.2,6]decan-8-yl methacrylate. (20 g, formula (I-1))
1H-NMR (CDCl3, 300 MHz) xcex45.95 (1H, brs), 5.41 (1H, brs), 2.35-2.00 (2H, m), 1.84 (3H, s), 1.84-1.51 (8H, m), 1.47 (3H, s), 1.46-0.80 (6H, m).
13C-NMR (CDCl3, 75 MHz) xcex4166.5, 137.4, 124.2, 86.4, 51.4, 46.6, 45.0, 40.6, 39.8, 32.4, 31.6, 31.1, 27.2, 25.5, 18.3. 
The procedure is as same as that of example 1 except methacryloyl chloride is replaced by acryloyl chloride (18.1 g). The product 8-methyl-tricyclo[5.2.1.02,6]decan-8-yl acrylate (18.5 g) (formula (I-2)) as colorless oil is obtained.
1H-NMR (CDCl3, 300 MHz) xcex46.19 (1H, dd, 17.3, 1.74), 5.90 (1H, dd, 17.3, 10.3), 5.61 (1H, dd, 10.3, 1.74), 2.29-1.44 (8H, m), 1.42 (3H, s), 1.40-0.84 (6H, m).
13C-NMR (CDCl3, 75 MHz) xcex4165.4, 129.8, 129.32, 86.6, 51.3, 46.6, 45.0, 40.6, 39.8, 32.4, 31.6, 31.2, 27.2, 25.5. 